The treatment of chronic disease often requires repeated and prolonged access to the vascular system. As it is impractical and dangerous to insert and remove a catheter at every session, patients are often fitted with a semi-permanent catheter which is left in place for months or years.
A valve may be used to seal the proximal end of such a semi-permanently implanted device when the device is not in use. One common type of valve is the Pressure Actuated Safety Valve (PASV), which open when a fluid pressure in the catheter exceeds a preselected threshold level. These PASV's often include a slitted membrane designed to remain closed when subject to pressures applied by the vascular system or through normal movement of the patient and to open when fluid pressure applied thereto to introduce fluids to or remove fluids from the vascular system.